Magneto-optic recording media with protective layer

Abstract

A protective layer for a magneto-optically active layer is formed of an outer impermeable layer and an inner layer that protects the active from the outer layer. The outer layer may be an oxide and the inner layer a non-oxide. The oxide and non-oxide layers may form discreet layers or they may be continuously graded. The graded layer may be formed by reactively sputtering aluminum in the presence of reactive gases, oxygen and nitrogen, while continually varying the flowing reactive gas from nitrogen to oxygen.

What is claimed is: 
     
       1. A magneto-optic medium having a recording layer of an active magneto-optic material and a protective layer thereon, comprising: a first material of said protective layer which is not in contact with the surface of said recording layer;   a second material of said protective layer adjacent to said surface of said recording layer;   said first material being a pure oxide composition material layer in its uppermost layer adjacent to the external surface of said protective layer;   said second material being a pure non-oxide composition material layer in its lowermost layer which is contiguous with said recording layer; and   said first and second materials in said protective layer being graded in composition continuously between the pure oxide uppermost and the pure non-oxide lowermost layers within said protective layer.   
     
     
       2. The magneto-optic medium of claim 1, wherein said active magneto-optic material comprises an amorphous alloy of a rare earth and a transition metal. 
     
     
       3. The magneto-optic medium of claim 1 wherein said first material is aluminum oxide and said second material is aluminum nitride. 
     
     
       4. The magneto-optic recording medium of claim 1 wherein said active layer material is a rare earth and transition metal alloy, and said second material is comprised of silicon nitride deposited by reactive sputtering of silicon nitride in a sputtering gas having a partial pressure of nitrogen to maintain stoichiometry. 
     
     
       5. The magneto-optic medium of claim 1, wherein said first material is an oxide material and said second material is a nitride material, said second material is directly deposited in high-purity phase on the active magneto-optic layer material, said first and second materials are graded continuously through said protective layer in a manner that said first material is directly deposited in high-purity phase at the end surface of the protective layer away from the active magneto-optic layer material. 
     
     
       6. A method for protecting an active layer for magneto-optic medium comprising reactively sputtering aluminum on said layer in the presence of Argon sputtering gas and partial pressures of the reactive gases, oxygen and nitrogen, and gradually varying the composition of the protective layer by varying the composition of flowing reactive gas gradually from nitrogen to oxygen to provide a non-oxide material adjacent said active layer and an oxide non-nitride surface of said protective layer away from said active layer. 
     
     
       7. The method of claim 6 wherein said active material comprises a magneto-optically active amorphous alloy of a rare earth and a transition metal. 
     
     
       8. The method of producing a magneto-optic medium comprising reactively sputtering a metal on an active layer, in the presence of reactive gas, on a magneto-optic material, and varying the composition of s id reactive gas during said sputtering to be initially comprised of nitrogen without oxygen, to deposit a non-oxide material at the surface of said magneto-optic material, and to be finally comprised of oxygen without nitrogen, to provide a protective layer with a non-nitride surface. 
     
     
       9. The method of claim 8 wherein said step of sputtering comprises sputtering aluminum.